diff --git a/components/application-mgt/org.wso2.carbon.device.application.mgt.store.api/src/main/java/org/wso2/carbon/device/application/mgt/store/api/services/impl/CommentManagementAPIImpl.java b/components/application-mgt/org.wso2.carbon.device.application.mgt.store.api/src/main/java/org/wso2/carbon/device/application/mgt/store/api/services/impl/CommentManagementAPIImpl.java
index 2ae8cb8b7e2..7c378162196 100644
--- a/components/application-mgt/org.wso2.carbon.device.application.mgt.store.api/src/main/java/org/wso2/carbon/device/application/mgt/store/api/services/impl/CommentManagementAPIImpl.java
+++ b/components/application-mgt/org.wso2.carbon.device.application.mgt.store.api/src/main/java/org/wso2/carbon/device/application/mgt/store/api/services/impl/CommentManagementAPIImpl.java
@@ -62,19 +62,17 @@ public class CommentManagementAPIImpl implements CommentManagementAPI {
         List<Comment> comments = new ArrayList<>();
         try {
             PaginationRequest request = new PaginationRequest(offSet, limit);
-            if (request.validatePaginationRequest(offSet, limit)) {
+            if (uuid == null) {
+                return Response.status(Response.Status.NOT_FOUND).entity("Comments not found").build();
+            } else if (request.validatePaginationRequest(offSet, limit)) {
                 commentsManager.getAllComments(request, uuid);
                 return Response.status(Response.Status.OK).entity(comments).build();
             }
-        } catch (NotFoundException e) {
-            log.error("Not found exception occurs to uuid " + uuid + " .", e);
-            return Response.status(Response.Status.NOT_FOUND).entity("Application with UUID " + uuid + " not found")
-                    .build();
         } catch (CommentManagementException e) {
             String msg = "Error occurred while retrieving comments.";
             log.error(msg, e);
-            return Response.status(Response.Status.INTERNAL_SERVER_ERROR)
-                    .entity(" Internal server error occurs").build();
+            return Response.status(Response.Status.INTERNAL_SERVER_ERROR).entity(" Internal server error occurs")
+                .build();
         }
         return null;
     }
@@ -142,15 +140,16 @@ public class CommentManagementAPIImpl implements CommentManagementAPI {
 
         CommentsManager commentsManager = APIUtil.getCommentsManager();
         try {
-            commentsManager.deleteComment(commentId);
+            if (commentId == 0) {
+                return Response.status(Response.Status.NOT_FOUND).entity("Comment not found").build();
+            } else {
+                commentsManager.deleteComment(commentId);
+            }
         } catch (CommentManagementException e) {
             String msg = "Error occurred while deleting the comment.";
             log.error(msg, e);
-            return Response.status(Response.Status.INTERNAL_SERVER_ERROR)
-                    .entity("Internal server error occurs").build();
-        } catch (NotFoundException e) {
-            log.error("Not found exception occurs to comment id " + commentId + " .", e);
-            return Response.status(Response.Status.NOT_FOUND).entity("Comment not found").build();
+            return Response.status(Response.Status.INTERNAL_SERVER_ERROR).entity("Internal server error occurs")
+                .build();
         }
         return Response.status(Response.Status.OK).entity("Comment is deleted successfully.").build();
     }
diff --git a/components/application-mgt/org.wso2.carbon.device.application.mgt.store.api/src/test/java/org/wso2/carbon/device/application/mgt/store/api/services/CommentManagementAPITest.java b/components/application-mgt/org.wso2.carbon.device.application.mgt.store.api/src/test/java/org/wso2/carbon/device/application/mgt/store/api/services/CommentManagementAPITest.java
index cd795abe091..e48346c9ae7 100644
--- a/components/application-mgt/org.wso2.carbon.device.application.mgt.store.api/src/test/java/org/wso2/carbon/device/application/mgt/store/api/services/CommentManagementAPITest.java
+++ b/components/application-mgt/org.wso2.carbon.device.application.mgt.store.api/src/test/java/org/wso2/carbon/device/application/mgt/store/api/services/CommentManagementAPITest.java
@@ -80,12 +80,23 @@ public class CommentManagementAPITest {
     @Test
     public void testGetAllCommentsInternalError() throws Exception {
         PowerMockito.stub(PowerMockito.method(APIUtil.class, "getCommentsManager")).toReturn(this.commentsManager);
-        Mockito.doThrow(new CommentManagementException()).when(this.commentsManager).getAllComments(Mockito.any(),Mockito.anyString());
+        Mockito.doThrow(new CommentManagementException()).when(this.commentsManager)
+            .getAllComments(Mockito.any(), Mockito.anyString());
         Response response = this.commentManagementAPI.getAllComments("a", 1, 4);
+        Assert.assertNotNull(response, "The response object is null.");
         Assert.assertEquals(response.getStatus(), Response.Status.INTERNAL_SERVER_ERROR.getStatusCode(),
             "The response status should be 500.");
         Mockito.reset(commentsManager);
+    }
+
+    @Test
+    public void testGetAllCommentsNotFoundError() throws Exception {
+        PowerMockito.stub(PowerMockito.method(APIUtil.class, "getCommentsManager")).toReturn(this.commentsManager);
+        Response response = this.commentManagementAPI.getAllComments(null, 1, 3);
         Assert.assertNotNull(response, "The response object is null.");
+        Assert.assertEquals(response.getStatus(), Response.Status.NOT_FOUND.getStatusCode(),
+            "The response status should be 404.");
+        Mockito.reset(commentsManager);
     }
 
     @Test
@@ -174,14 +185,22 @@ public class CommentManagementAPITest {
     @Test
     public void testDeleteCommentInternalError() throws Exception {
         PowerMockito.stub(PowerMockito.method(APIUtil.class, "getCommentsManager")).toReturn(this.commentsManager);
-        Mockito.when(this.commentManagementAPI.deleteComment(Mockito.anyInt()))
-            .thenThrow(new CommentManagementException());
+        Mockito.when(this.commentManagementAPI.deleteComment(1)).thenThrow(new CommentManagementException());
         Response response = this.commentManagementAPI.deleteComment(1);
         Assert.assertNotNull(response, "The response object is null.");
         Assert.assertEquals(response.getStatus(), Response.Status.INTERNAL_SERVER_ERROR.getStatusCode(),
             "The response status should be 500.");
     }
 
+    @Test
+    public void testDeleteCommentNotFoundError() throws Exception {
+        PowerMockito.stub(PowerMockito.method(APIUtil.class, "getCommentsManager")).toReturn(this.commentsManager);
+        Response response = this.commentManagementAPI.deleteComment(0);
+        Assert.assertNotNull(response, "The response object is null.");
+        Assert.assertEquals(response.getStatus(), Response.Status.NOT_FOUND.getStatusCode(),
+            "The response status should be 404.");
+    }
+
     @Test
     public void testGetStars() throws Exception {
         PowerMockito.stub(PowerMockito.method(APIUtil.class, "getCommentsManager")).toReturn(this.commentsManager);
@@ -195,7 +214,8 @@ public class CommentManagementAPITest {
     @Test
     public void testGetStarsCommentError() throws Exception {
         PowerMockito.stub(PowerMockito.method(APIUtil.class, "getCommentsManager")).toReturn(this.commentsManager);
-        Mockito.when(this.commentManagementAPI.getStars(Mockito.anyString())).thenThrow(new CommentManagementException());
+        Mockito.when(this.commentManagementAPI.getStars(Mockito.anyString()))
+            .thenThrow(new CommentManagementException());
         Response response = this.commentManagementAPI.getStars("a");
         Assert.assertNotNull(response, "The response object is null.");
         Assert.assertEquals(response.getStatus(), Response.Status.INTERNAL_SERVER_ERROR.getStatusCode(),
@@ -255,7 +275,7 @@ public class CommentManagementAPITest {
         Response response = this.commentManagementAPI.updateStars(3, "a");
         Assert.assertNotNull(response, "The response object is null.");
         Assert.assertEquals(response.getStatus(), Response.Status.CREATED.getStatusCode(),
-            "The response status should be 200.");
+            "The response status should be 201.");
         Mockito.reset(commentsManager);
     }